Arrange the digits 0 to 9 such that the number formed by the first digit
is divisible by 1, the number formed by the first two digits is divisible
by 2, that formed by the first three digits divisible by 3, and so forth;
thus the number formed by the first 9 digits will be divisible by 9 and
that formed by all 10 digits divisible by 10.

The number's nine digits contain all the digits from 1 to 9. When read
from left to right the first two digits form a number divisible by two,
the first three digits form a number divisible by three...

In a 6-digit number, the sum of the digits is 43, and only two of the
following three statements about the number are true: (1) It's a
perfect square. (2) It's a perfect cube. (3) It's less than 500,000.

There are 35 different sets of 7 prime numbers that sum to 100. Of
those sets, which has the largest product, and which has the largest
number? I'm using trial and error and it's very frustrating. Is there
a better way?

Four dogs are at four corners of a field. Each dog chases the dog to its
right; all four run at the same speed and no acceleration is assumed.
Where will they meet, and how long and how far will they have run when
they meet?

Two people are trapped in a small freezer that is slowly getting
colder and colder... Is it possible for them to escape? If so, how?
What’s the maximum number of minutes required to escape given ANY
initial combination of button states?